Mount Prospect, Illinois 7 Day Weather Forecast

Wx Forecast - Wx Discussion - Wx Aviation

227
FXUS63 KLOT 171146
AFDLOT

Area Forecast Discussion
National Weather Service Chicago/Romeoville, IL
646 AM CDT Tue Mar 17 2026

.KEY MESSAGES...

- A clipper-like system will lead to a coating of snow tonight
  through Wednesday morning. Untreated surfaces may become
  slippery.

- Another clipper system may deliver rain showers on Thursday.

- Temperatures will warm toward the 60s to locally lower 70s
  Friday and Saturday. A cold front will move through the area
  at some point on Sunday.

&&

.DISCUSSION...
Issued at 134 AM CDT Tue Mar 17 2026

Outside from one last narrow (1-mile wide) convective-like band
of snow moving through northern Illinois and northwestern
Indiana early this morning, the blowing snow event has largely
come to an end. Gradually clearing clouds from the north,
continued low- level cold air advection, and a fresh snowpack
(especially across northwestern Illinois) will set the stage for
a chilly morning. Temperatures at daybreak are expected to
range from the low single digits northwest to the low to mid
teens southeast. When combined with the wind, it will feel more
like minus 10 to around 0 out there. Bundle up when heading out
the door this morning!

Today looks relatively quiet in the weather department. A
surface pressure ridge currently centered west of the
Mississippi River will shift eastward today, leading to winds
deceasing in magnitude and shifting in direction to be out of
the southwest. While a few clouds may linger south of I-80 at
sunrise, most areas should have a sunny start to the day. A
relatively cold start and an increase in upper- level clouds
this afternoon will set the stage for an unseasonably cool day
with highs generally in the 20s.

Tonight into Wednesday the first half of Wednesday, a clipper-
like system will race from the northern Plains to the Great
Lakes. A region of low-level warm air advection on the south
side of the clipper system will support the development of a
broad region of snow, which will track more or less directly
over our area tonight. Relatively modest forcing (peak omega of
minus 4 to 5 ubar/sec) points toward a 4 to 8 hour period of
relatively modest snow rates (0.1 to 0.2"/hr), leading to one
half to perhaps just over an inch of snow across the area by the
time snow tapes between daybreak and noon. Snow character will
start somewhat fluffy with ratios near 20:1 before the warming
low-level thermal column trends ratios closer to 10:1 through
the event. In the absence of meaningful wind (southerly gusts
perhaps intermittently hitting 20 mph), the snow tonight through
early Wednesday should largely be a slippery travel threat on
secondary or untreated roads. Clearing skies, warming
temperatures to the upper 30s to mid 40s, and the increasingly
strong March sun angle should help melt most of the snow during
the afternoon.

Thursday carries above average forecast uncertainty as ensemble
guidance advertises another clipper system moving through the
general region though with spread on the track and quality of
moisture. Outcomes in which the clipper moves directly overhead
with quality moisture are characterized by rain showers and
highs limited to the upper 30s to perhaps lower 50s, warmest
southwest. Meanwhile, outcomes in which the clipper misses our
area entirely to the north would support mostly sunny skies and
highs racing into the mid 60s. We`ll take the middle ground
approach for now and advertise low (10- 30%) chances for rain
showers, and highs in the mid 40s to low 60s.

Toward the end of the week and into the weekend, the incredibly
anomalous upper-level ridge responsible for record- breaking
heat across the southwestern United States will shift eastward,
leading to a warming trend in the Great Lakes. Ensemble mean
highs Friday and Saturday soar into the 60s and even lower 70s
(though we`ll have to keep an eye on a backdoor front which may
drop temperatures in northeastern Illinois and northwestern
Indiana Friday afternoon). Thereafter, still am seeing a signal
for a strong upper-level shortwave to drive a cold front through
the Great Lakes on Sunday, leading to cooler temperatures
(upper 40s to lower 50s?) to start next week. With that said,
ensemble guidance supports temperatures returning to above-
average values by the middle of next week.

Borchardt

&&

.AVIATION /12Z TAFS THROUGH 18Z WEDNESDAY/...
Issued at 646 AM CDT Tue Mar 17 2026

Key Messages:

- Another period of snow with IFR/MVFR visibilities and ceilings
  is expected late tonight/early Wednesday morning.


Precipitation-free and VFR conditions are expected to prevail
during the daytime today. Still couldn`t rule out that MVFR
ceilings are briefly attained at the Chicago metro terminals as
cumulus clouds initially develop this afternoon before cloud
bases lift above 3000 ft AGL, but it`s more likely that cloud
bases will begin and stay above this level or that low-based
cloud coverage ends up remaining FEW or SCT. Winds will
gradually back from a west-northwesterly to a south-southwesterly
direction over the course of the day and into the evening
before prevailing from a southerly direction overnight into
Wednesday morning.

Another period of snow is expected late tonight into early
Wednesday morning as an upper-level disturbance drops through
the region. IFR visibilities are likely to be observed during
the steadiest periods of snowfall, and ceilings are likely to
drop down to MVFR levels as well. Cold temperatures in the 20s
and upper teens will allow for snow to accumulate on all
surfaces, though only around 0.5 to 1.5 inches of snow
accumulation is expected in total before the snow tapers off
around sunrise Wednesday morning.

Ogorek

&&

.LOT WATCHES/WARNINGS/ADVISORIES...
IL...None.
IN...None.
LM...Small Craft Advisory until 10 AM CDT this morning for Winthrop
     Harbor IL to Gary IN.

     Small Craft Advisory until 3 PM CDT this afternoon for Gary to
     Burns Harbor IN-Burns Harbor to Michigan City IN.

&&

$$

Visit us at weather.gov/chicago